Means for and method of regulating the transmission over electric circuits



ii atented Der, 12, 1922.

entree stares "ea-rear ALVA a CLARK. or BROOKLYN, new Yam. ASSIGNOR T amnmcan rnmrnonn nn TELEGRAIJH COMPANY, aconronarzon oannw roan.

MEANS eon AND ran-"r1101; or REGULATING THE reanstarssron oven ntnc'rare CIRCUITS,

Application filed September To all whom it in (1y conce r21 Be-it known that 1, AMA B. (LARK, re-

I siding at Brooklyn. in the'county of Kings and State of New York, have invented certain Improvements in Means for and Methods of Regulat ng the Transmission ot er Electric (ir'cuitsof which the following is a specification. I

This invention relates to transmission circuits. and more particularly to transmission circuits of the type known as four-Wire circuits, although it is in general applicable "to transmission circuits of any kind.

The princi mlobject ot the invention is to provide suitable methods and means for maintaining substantially constant the transmission equivalent of a circu t regardless of variations in the conditions affecting the electrical characteristics of the circuit. Other and further objects will, however. be clear from the description of the invention hereinai'tcr given.

In general, the transmission equivalent of a circuit varies. due to a number of clifierent causes. Tf the transmission circuit he of the t'our wire type, in which a pair of separate transmission lines are employed for trans: mitting in opposite directions, these causes may be divided into two classes: Thetirst class comprises causes which affect both sides of the circuit, or in other worilsfhoth trans.- mission lines, inthe same manner. Among these causes may he enumerated variations in the resistance of the conductors, loaxlingcoilis, V

ctingvariatimis in capacity, inductance, or other electricalclniracter st-ics the cable, and variations in the potential of repeater batteries common to repeaters in both sides.

of the circuit. The second class comprises causes which afiect the two sides tlifierently, such as variations in the structure of repcatcr bulbs where v'acuumtube repeaters arc cmploycih variations in. the potentials of grid batteries. or accidental variations due to the resistance of bad jointsgleakzige due to poor insulation, etc.

in the case of transmission eircu'itsin. which only one transmission line 'is nsetl for transmission in the two directions, the factor of variation with respect to the'two sides of the circuit will be absent. but some or all of the above causes may contribute to produce variations in the transmission 10, 1918. Serial No. 253,413?.

The present invention contemplates eliminating these d-iiliculties by varying some adjustable element of the t'ansmission "air-- cuit to compensate for the variations introduced into the circuit. In general a number of methods may be employed in carrying out the objects of this invention. For

example, the etfects clue to some one cause,"

such as temperature variations, may he cornpensate'd for by observing the changes prm tluccd in one circuit of a cable and. then varying in accordancewith such changes, siniilar-elen'ients ofa number of circuits which are affected in a like manner. In

-. equivalent of thecircuit, thereby rendering the case of av four-wire circuit, where it is desired to take into account variations which do not affect both sidesof thecircuit alike, adjustment may he made for each side of the four-wire ciruit separately to ecannensate for all causes of the variation inveither side. Where less precision is required, effects clue to all possible variations in the two sides of the four-wire circuit" may be compensated for,

by simultaneously varying like elements in the two sides of the circuit on the assump tion that the two sides vary alike,

'lhesejnethods may be carried-out either manually or automatically aincth'y milk:

lug adjustments either constantly with veri ations' in-th'eleircnit. or at intervals of suitable frequency: vFor purposes of illustration, apparatus is disclosed for automati- (fillY-xtifl'llj'illfi out the lastmethod above mentioned; but it will he linaerstood that manual apparatus maybe erngiloye'tl if'de sired. I I

The objects of the invention are sectir'erl as hereirr'disclosed by, disconnecting the ends of the two transmission lines. comprising a four-wire circuit,- lirom theisterminating arrangements, and interconnecting; the ends through adjustabletransmission devices capable of introducingtransmission losses or gains, which together are adjusted to have a transmission equivalent double and opposite insign to that to which the sidesot the 'tmir-wire circuit. exclusive of the terminals, are to be adjusted. The path thus formed will sing when the amplification therein exceeds the loss, and the cir nit will have the proper transmission equivalent when it is adjusted to a criticsi point at which singing just begins or ceases. Accordingly. hy arbitrarily bringing); the equivalent of the path well below the singing point. and then gradually adjusting the circuit until singing just begins. or by raising the equivalent well above the initial singing point and cr minally adjusting: the circuit until singing just. ceases. the circuit will he set For the proper transmission equivfiltfflt. This may be accomplished by arl: jnsting transmission elements in the transmission lines themselves.

here the former method is employed, the amplification in the closed path may he reduced until it is less than the total loss preferably by decreasing the amplification of one-"uy-repeaters in the two transmission lines of the four-wire circuit. By then gradually increasing the simplification of the similar amplifiers in two UfinSZIllS- sion lines until singing commences, which occurs when the total aim '"icatiou. is approximately equal to the total ioss. the four-wire circuit will he set for the desired transmission equivalent. In ortier to per form these functions automatically, the circuit may be so arranged that when the two ends of the four-Wire circuit are intercom nectetl, an automatic switch controlling the setting of the potentiometers which deter" mine the amn iiiention of the repeaters, will be restored t.) a normal condition in which the otentiometers are set for the least possible u n inflection. The-switch than he -ins to advance. gradually adjusting the potentiomoters, and thereby increasing the amplification until a point is reached at which singing commences. An niternnting current reey. responsive to the singing oscillations,

i -"i'v then he arren ed to sto the motion of the witch, so that the circuit remains mijusteci at the critical point at which singing just commences.

The. invention may now he more fully oncl 'stood from the toilowing clescription when .renol in connection with the 21080121 panying (hinting; Figure ll of which is a. schematic diagram of an arrangement in which the invention. may be embodied. while Figure 2 is ii circuit iagram showing on automatic apparatus forcerrying out the invention, as applied to e tour-wire circuit.

Referring to Figure 1,21 four-wire circuit is shown interconnectingtwo terminal sta 10115 C and D. said four-Wire circuit comprising a pair of transmission lines L end li for transmitting in opposite directions. it will understood that these transmission iines n 3, include one way repeaters (not shown; for securing the, desired transmission over the circuit. At the terminal station the tour-wirocircnit may he cssoeisteo by means of the usual three-Winding transformers i and 2, with terminating: two-wire lines L and L said two-Wire lines being linlun eii lay suitable artificial lines N and N When In it is desired to adjust the transmission of the tonnn circuit the ends of the lines L and L may be disconnected from their terminal arrangements by means of relays 3. l, 5 tillKi (3. only the contacts of which are shown in Figure 1. By means of these rehr' 's the ends of the lines l tiiltl L, may he intercom-- necteil through the adjustable transmission devices hi, and M indicated schenmticuliy. These devices may he of nny suitable character and should. he so designed as to have ii. total transmission equivalent whose value is double and opposite in sign to, that to which it is desired the sides of the min wire circuit exclusive of the terminal apparatus shall be adjusted. in. other WQNiS. it it is desired to or ange the foiir-i'vire circuit so that each of two will give a eeriilli. gain in transmission. the devices iii. and iiishould t ther re 7 .nt :1 trintismission loss equal to L'WLCG th' iicsired gain. On the other hand, it is desired that there shall he a certain transmission loss in each of the two sides. the cleric-es M and M should coniprise amplifiers, or other inc-tins whereby a total transmission gain equal to twice the desired loss may he produced. in order to simplify the iiimngernent the devices M and M may be combined at one station as shown in Figure 2 so that at the other sta- Y tion the ends of the transmission lines L and L are directly connected. in order to adjust the transmission equivalent of the four-Wire circuit. transmission vnryii'ig devices X and IL which will give either loses or gains he provided in lines L and L respectively. These devices should first he set so as to make the nn'ipliiiczition less than the loss in the closed. path through M M L L X and X, so that singing does not take piece. The transmission devices K and may then be adjusted either minim ally or automatically, until the nnxpliticzn tion is equal to or hut sligifiiy greater than the loss, whereupon singing; oscillations are. set. up in the circuit. The oscillations ectoate the device V to indicate to the operator that the proper adjustment has been reached in the use of n manual adjustment, or to ontoineticnily stop further adjustment where ti Es M one. M Assuming that the o e- "2716M M anti iii i been properly set, the

Lesaeeo an four-wire circuit will now have the desired transmission equivalent.

Turning now to Figure 2, which shows in more detail an arrangement corresponding to that illustrated schematically in Figure 1,

it will be seen that amplifiers A and A; are inserted in the line L -and L, respectransmission lines L and Lyfrom the terminating arrangement at stations and. ID, and for interconnecting the ends of said lines in order to regulate the transmission thereof. At station 0 the lines L and L may be directly connected over path '2'. At station D the ends of these lines-are interconnected through an adjustable transmission'devicecomprising an amplifier A corresponding.

to the device M of Figure 1. A stepping magnet 8 is provided to control the advancement of the switch including wipers S and S Bridged across the path including the.

' amplifier A is an alternating current relay which responds to singing over the foura'ire circuit to open the circuit of the stepping magnet and bring the switch to rest.

he relays 3, 4, 5 and 6, as well as relay 9, are included serially in a simplex circuit passing over the two sides of the line In.

Any other suitablecircuit connecting the terminals of the four-wire circuit may, of course, be employed. This circuit is normally closed but is opened by means. of switches 10 and 11 Which may be operated in a manner well understood in theart when connections are completed over the two-wire lines L and L to the four-wire circuit,

thereby die-energizing relay 9, and relays 3,

4, 5 and 6. Relays 3, 4,5 and 6 upon being (ls-energized, connect the "r'our-wvire circuit to the terminal arrangement. The simplex circuit controlling these relays may also be opened by means of a switch 12 which may be either hand operated, or may be operated at regular intervals by means of a suitable timing arrangement. When the simplex circuit is again closed upon the taking down of the connection ovcrlines L, and L or by the closing of switch 12, the relays 3, 4, 5 and 6 again disconnect the four'wire circuit from the terminal arrangement and interconnect the ends of the lines Lyand 1D,. The relay 9 at the same time advances a commutator arrangement one step so that the brush thereof passes o A a live segment of the commutator and sends a momentary impulse through the release magnet 14: of

the potentiometer controlling switchto restore said switch to its normal position, in

which position the potentiometers are set for the lowest degree of amplification. The

releasemagnet 14 also opens the locking circuit of the alternating current relay V,

which is normally locked up. thereby permitting the stepping magnet 8 to advance the switch until singing just begins. The alternating currentrelay V responds to the singing oscillations and brings the switch to rest, at the same time closing a locking circuit for itsown Winding through a .bat-

tery 16, a i

Assuming that the amplifier A, has been properly adjusted, as explained, upon com pleting a connection over lines L, and L the switches 10 and 11 will be opened, thereby breaking the normally closed circuit cuit may be traced from. battery, over switch 10,1switch12, through the windings of relays 6 andS, thence in parallel over the two conductors of the transmission line L through the' windings of relays 9, "5 and 4C, and over switch 11 to ground. Relays 3, 4, 5 and 6 release their armatures so that the ends of the transmission lines L and L, are

through relays '3, 4, 5, 6 and 9. This ci rconnected through the transformers 1 and 2 1 to the terminating two-wire lines, 'and conversation may nowtake place over the fourwire circuit. The release of magnet'9 permits its armature to retract and engage a new tooth of the commutator arrangement 13, but no circuit change results therefrom.

When the connection over lines L, and L is taken down, switches 10 and 11 are again closed to complete the simplex circuit al ready traced through relays 3, 4, 5 and 6, and through magnet 9. Relays 3, 4, 5 and 6 disconnect the transmission lines L, and L from the-terminal arrangements and interconnect the ends of said lines through the the ratchet wheel of the switch $55, per

mitting the switch to be restored to its nor- The release magnet 14 also opens the locking circuit of the alternating current relay V which may be traced from the battery 16 through the winding and over the right hand frontconta-ct otsaid relay, and over the back contact of release magnet 14- baclr to battery. The rela V is thereby de-energized and at its left liand back contact commal condition, as indicated in the diagram.

pletes a circui from ground throughinterrupter 15 through the winding of stepping magnet 8 to battery. Stepping magnet 8 now advances the switches S, and S step lay step, so that the amplification of the amplilicrs A, and A, is ,gradually increased until thc gains due to these amplifiers are sullicicntly high to make the total amplification in the closed path as shown on Figure 1, equal to or slightly greater than the total loss in this path, whereupon singing will take place. The alternating current relay V operates in response to the singing oscillations, thereby opening the circuit of the stepping magnet 8 and bringing the switches H, and S, to rest. The alternating current rcla V at its right hand front contact completes the locking circuit previously traced through the battery 16, so that said relay remains locked up until such time as the process of adjustment may be again repeated. The loclfngcircuit of the relay V is of low resistance, and is a direct shunt across the output circuit of the amplifier A, which forms part of the closed path in which sing inn; is taking place. The shunt thus established causes singing to cease, and the switches s, and S, now remain adjusted so that the transmission equivalent of each of the lines 113 and L exclusive of their terminating arrangements is opposite in sign to, and equal to one-half that of the amplifier A ll, therefore. the amplifier A has been properly set, the four-wire circuit will have the desired transmission equivalent. The potentionieters l ,v and P, will remain in their set positions, and the circuit is now in condition to he used.

The same result may be secured by opening: and again closing the switch 12 either manually or by means of a time controlled device. it will also be obvious that the automatm switch arrangement may be eliminated. if desired, and the adjustment of the potcntiomcters may he performed manually.

By means otthe arrangement disclosed, a tour-wire circuit may be adjusted so that it will have any desired transmission equivalent. regardless of variationswhich may take place in the circuit. so long, as the variations ail'cct both sides of the circuit alike. it Will also he obvious that the general principles herein disclosed may be cmhodied in many other organizations widely different from those illustrated. Without departing from the spirit (at the invention as defined in the following claims.

What is claimed is:

'l. The method of adjusting the transmission ciliciency of a circuit consisting of a pair of transmission lines for transmitting in opposite directions, which consists in connecting the ends oi said pair of lines together. increasingthe loss in the circuit thus produced so that singing does not take place. and gradually decreasing the loss until singingjust commences.

'ihe method oi adjusting the trans i see-sac mission efiiciency of a circuit consisting of a pair of transmission lines for transmitting in opposite directions, and each includii'ig amplifying means, which consists in connecting the ends of said pair of lines though transmission devices having a total. transmission equivalent double and opposite in sign to that to which it is desired to adjust each side of the our Wire circuit, decreasing the amplification of said amplifying means so that singing does not take place over the circuit thus produced, and grad ually increasing the amplification 11 Ml singing just commences.

3. The method of adjusting the transmission efficiency of a circuit consisting ot a pair of transmis lines for transmitting in opposite direc ans, which consists in connecting the end. said pair of lines together through ansmission devices having a total transri. on equivalent opposite in sign and twic sired to adjust each side of the our wire circuit, increasing the loss in the circuit thus produced so that singing does not take place, and gradually decreasing the loss until singing just commence 4:. The method of adjusting the trans mission etiiciency of a circuit consistingof pair of transmission lines for transmitting in opposite directions and each including amplifying m62iZlS,'Wl1lCll consists in corn necting the ends of said pair of lines toainplifying means so that singing does not take place over the circuit thus produced, and gradually increasing the amplification until singing just commences.

5. In a signaling system, a tour \vir'etra-nsmission circuit including a pair of transmission lines for transmitting in opposite directions, means to interconnect the ends of said lines independently of terminal connections, and means to increase the loss of said lines so that singing does not take place over the circuit thus formed and to gradually decrease the loss of s.v lines until singing just commences.

6. lo a signaling system, a circuit including a pair of transmis ion for transmitting in opposite directions, means to interconnect the ends of said lines, means to increase the loss of said lines so that singing. does not take place over the circuit thus formed, means to gradually de crease the loss of said lines until singing just commences, and means responsive to the singing thereby produced to render said last mentioned means inactive.

7. In a signaling system, a transmission circuit including. a pair of transmission lines for transmitting in opposite direc tions, amplifying means in said lines independently of terminal connections, means to interconnect the ends 0? said lines, means at to which it is do gether, decreasing the amplification of said iii) ' equivalent double 40 ,to gradually increase sion lines may be connected, meansto to decrease the amplification of said amplifying means 'so that singing does not take place over the circuit thus formed and to gradually increase the amplification until singing just commences.

8. In a signaling system, a transmission circuit including a pair of transmission lines for transmitting in opposite directions, amplifying means'for said lines, 'means to interconnect theends of said lines, means to decrease the amplification of said amplifying means so that singing does not take place over the circuit thus formed, means the amplification until singing just commences, and means responsive to the singing thereby produced. to render said last mentioned means inactive.

9. In a signaling system, a transmission circuit including a pair of transmission lines for transmitting in opposite directions, means to interconnect the ends of said lines through a transmission device having; a transmission equivalent opposite in sign and double that to which it is desired to adjust each side of the c rcuit, means to increase *the loss of said lines so that singing does not take place over the circuit thus formed, means to gradually decrease the loss of said lines until singing" just commences, and

means responsive to the singing thereby produced torender said last mentioned means inactive.

10. In a signaling system, transmission circuit including a pair of transmission lines for transmitting in opposite directions, amplifying means for "said lines, means to interconnect the ends of said lines through a transmission device having a transmission and opposite in sign to that to which it is desired to adjust each side of the circuit, means to decrease the amplification of said amplifying means so that singing does not take place over the circuit thus formed, means to gradually-increase the amplification until singing just commences, and means responsive to the singing thereby produced to render said last mentioned means inactive.

11. In a signaling system, .a four wire transmission circuit including a pair of transmission-lines for transmitting in oppos site directions, terminating two wire lines to which the ends of said pair of transmisdisconnect said pair of transmission linesfrom the terminating two wire lines and interconnect the ends thereof through a. transmistion until singing 1 'an automa sion device having a transmission equivalent double and opposite in sign to that to which it is desired to adjust each side of the four wire circuit, means to increase the loss in the four wire circuit so that singing does not take place over the circuit thus formed, means to gradually decrease the loss until singing just commences, and means responsive to the singing thereby produced to render said last mentioned means inactive.

-12.'In a signaling system, a four wire transmission circuit including ,a pair of transmission lines for transmitting inopposite directions, amplifying means for said lines, termii'iating two wire lines to which the ends of said pair of transmission lines may be connected, means to disconnect said pair of transmission lines from the terminating two wire lines and interconnect the ends thereof through a transmission device having a transmission equivalent double and opposite in sign to that to which it is desired to adjust each side ofthe four wire circuit, means to decrease the amplification of said amplifying means so that singing does not take place over the circuit thus formed, means to gradually increase the amplifica- 'ust commences, and means responsive to the singing thereby produced to render said last mentioned: means inactive.

13. In a signaling system, a transmission circuit including a pairof transmission lines for transmitting in opposite directions, amplifying means for said transmission lines,

tic switch having a normal position and being adapted to be advanced therefrom or released and .restored thereto,means under the control of said switch for determining the amplification of said amplifying means, means to interconnect the ends of said transmission lines and to release said switch, means responsive to the release of said switch for decreasing the amplification of said amplifying means so that singing does not take place over the circuit formed by interconnecting said pair of transmission lines, means to gradually increase the amplification until singing just commences, and means responsive tothe singing thereby produced to bring said switch to rest.

In testimony whereof, I have signed my name to this specification this sixth day of September 1918.

ALVA B. CLARK. 

